As this type of X-Y table actuator, one disclosed in WO 2005/124789 (Patent Document 1) is conventionally known. The X-Y table actuator disclosed in Patent Document 1 includes a stationary plate to be fixed to a bed, a column, or the like, an intermediate plate freely movable in an X-direction with respect to the stationary plate, and a movable plate freely movable in a Y-direction with respect to the intermediate plate, where the three plates are stacked so that the movable plate is freely movable in the X-direction and in the Y-direction with respect to the stationary plate.
The stationary plate and the movable plate respectively include an accommodation groove and are formed into a channel-shape, whereas the intermediate plate is formed into a rectangular shape so as to be loosely fitted to the accommodation grooves. The lower half of the intermediate plate is assembled to the accommodation groove of the stationary plate through numerous balls so as to freely move in the X-direction in the accommodation groove. The upper half of the intermediate plate is assembled to the accommodation groove of the movable plate through numerous balls so that the movable plate freely moves in the Y-direction with respect to the intermediate plate. The movable plate at the highest level thus can freely move in the X-direction and in the Y-direction with respect to the stationary plate at the lowest level.
Patent Document 1 also describes an ultrasonic linear motor using a piezoelectric element as a means for moving the intermediate plate forward and backward in the X-direction with respect to the stationary plate by an arbitrary amount, and moving the movable plate forward and backward in the Y-direction with respect to the intermediate plate by an arbitrary amount. The ultrasonic linear motor is formed of a stator that produces a traveling wave by the piezoelectric element, and a movable element which is made of a thin metal plate and constitutes a traveling surface for the stator. The stator is arranged in a housing chamber formed in the intermediate plate, and the movable element is attached to the movable plate or the stationary plate at a position facing the stator, thereby constituting a drive means in the X-direction and a drive means in the Y-direction.